.father {
  color: red;
  width: 1.81333333rem;
}
.father .son {
  background-color: pink;
}
#header {
  width: 10px;
  height: 20px;
}
/*aaaaaaa */
.father {
  width: 30px;
  height: 80px;
  /* 除法需要加小括号  转rem */
  width: 8.25rem;
  background-color: #112244;
}
